Brazil is battling to contain an outbreak of the Zika virus which has been linked with birth defects and paralysis-causing Guillain-Barre syndrome. The United States Centres for Disease Control and Prevention has warned pregnant women against travelling to Brazil and 21 other countries where the virus is present, reports Xinhua.

Officials in Rio said measures are being taken to prevent the accumulation of stagnant water which is a breeding ground for the Aedes aegypti mosquito that carries the virus.

"Rio 2016 will continue to monitor the issue closely and follow guidance from the health ministry," the organising committee said in a statement.

The Olympics will be held from August 5 to 21, during Brazil's dry season, and officials say this will mean the mosquito is less prevalent. The Zika outbreak also comes as Rio prepares for its annual carnival celebrations which begin on February 5.

According to Nancy Bellei, the coordinator of clinical virology at Brazil's Infectious Diseases Institute, current high humidity meant tourists faced greater risk.

"This is the worst time to deal with an epidemic of a virus we know very little about. The government is trying to raise awareness and fight the mosquito but we won't achieve control in the short term under the current circumstances," she said.

Bellei added that the virus could easily spread to other countries by infected visitors.

"If a person is infected and then travels to a country where the Aedes mosquito is present, the mosquito can bite the person and thereby introduce the virus in a place where it previously did not exist," Bellei said.

Zika originated in Africa and is thought to have spread to Brazil by tourists in 2014. Local health officials say the mosquito is behind a rise in the incidence of microcephaly, a condition that causes unusually small infant head size. It can lead to stillbirths and long-lasting health problems for survivors.

Brazil has recorded 3,893 suspected cases of microcephaly since October. Less than 150 cases were reported in the country in 2014. The health alert coincides with Brazil's worst recession in decades, exacerbated by a sprawling corruption scandal at state-run oil company Petrobras.

Rio is also struggling to finish a raft of infrastructure projects in time for the Olympics, including a new subway line and several event venues. In addition, organisers have cut about $500 million in expenses while Rio's sailing and rowing venues face ongoing pollution concerns linked to the city's inadequate sewage system.